What are the benefits of stakeholders contributing?

(This post contains affiliate hyperlinks. Please read my full disclosure.
I recently read Project Stakeholder Management, Pernille Eskerod, and Anna Lund Jepsen (part Gower’s Fundamentals series on Project Management). It discusses why stakeholders are important to projects.
It might seem obvious to you. Your project sponsor is likely the person who made this project possible in the first instance, and has an interest in seeing it succeed. All stakeholders, including the sponsor, don’t have a duty to play nice. They can either help or hinder your project.
Jepsen and Eskerod say that stakeholders must weigh the pros and cons of a project before they make a commitment.
Both the expected benefits and the costs of these consequences are discussed.
What other people think about their involvement
Obstacles to making a contribution

They may not be able to go through the list and make conscious choices. It can be very confusing and they may not even realize it. They will decide whether to contribute or not, and how much, based on these thought processes, no matter how chaotic or unconscious.
Assessing the consequences
Because it hasn’t happened yet, project stakeholders can’t know how the project will turn out. They don’t have all of the information they need to make informed decisions about the potential consequences of their participation in the project. Instead, they will use their perceptions of the consequences to make a decision.
Their involvement could have positive or negative consequences. Participation has both benefits and costs. These benefits include:
Participation in a high-profile, high-status project
Increased exposure to senior executives
They can see tangible results in their department, such as new software or project deliverables.
Being able to influence the direction of the project by being an early adopter, rather than accepting changes after the pilot is completed – getting in on ground
Acquiring more skills for their team members or themselves
For themselves and their team members, career progression.

The other side of the equation is the cost, which they will have to “pay” in order to participate in the project like:
Offer of resources in the form people or services
To fund the project, they will need to take money from their budget
The time commitment
Administrative overheads associated with participating in a project
If the project goes wrong, there is the potential for negative publicity and a negative impact on their careers.

Stakeholders will mentally go through each one and make a decision about what is best for them. There are likely many other factors that could affect a stakeholder’s willingness to participate in a project. You can work with any stakeholder to identify the problem and work together to resolve it.
Concerns about contributing
Some people are keen to help others but feel that something is keeping them back, either consciously or unconsciously. One of these things could be how other people think.
Peer pressure is a common problem in office environments. What other people think of their involvement in the project will be part of the decision-making process for stakeholders. To help them make the right decision, encourage them to see their contribution as something they would naturally or logically do. This assumes that you want them to contribute! You could also encourage them in the opposite direction, but I don’t think they would be able to see it that way.
Stakeholders should also consider influences outside of the project. You could lobby others around you to get positive messages from them